THE INFLUENCE OF SPECIMEN GEOMETRY ON THE J-INTEGRAL R-CURVES FOR A FERRITIC STEEL

For a ferritic construction steel similar to St37-2 the cross section of three-point bend type specimens was selected to be B : w = 1 : 2 an d 1 : 1 (B : thickness, w : specimen width, and w = 25 mm was kept con stant). For these two geometries the onset of stable crack growth J0 w as found to be identical, the slope of the J-integral R-curves reveale d only small differences. A small size defect in the microstructure of one specimen delivered a pronounced change in the tearing modulus. Th e reserve in stable crack growth is small. The results of this materia l is compared with the results obtained earlier for the nuclear grade material A 533 B1 in connection with different crack length to specime n width ratios.